SA033-02
Global modeling of magnetosphere-ionosphere coupling at the limit of the fluid approximation: Auroral beads and ballooning-interchange instability in the magnetosphere
Tuesday, 15 December 2020: 17:38
Virtual
Kareem Sorathia1, Viacheslav G Merkin2, Evgeny V Panov3, Binzheng Zhang4, John Lyon5, Aleksandr Ukhorskiy6, Jeffrey Garretson7, Adam Michael8, Shinichi Ohtani9, Mikhail I. Sitnov9, Michael James Wiltberger10, Frank Toffoletto11, Dong Lin12, Shanshan Bao13 and Kevin H Pham14, (1)Johns Hopkins University Applied Physics Laboratory, Laurel, MD, United States, (2)The Johns Hopkins University, Laurel, MD, United States, (3)Organization Not Listed, Washington, DC, United States, (4)High Altitude Observatory, Boulder, CO, United States, (5)Dartmouth College, Hanover, NH, United States, (6)Johns Hopkins University Applied Physics Laboratory, Laurel, United States, (7)Applied Physics Laboratory Johns Hopkins, Laurel, United States, (8)Boston University, Boston, MA, United States, (9)JHU/APL, Laurel, MD, United States, (10)National Center for Atmospheric Research, High Altitude Observatory, Boulder, CO, United States, (11)Rice University, Department of Physics and Astronomy, Houston, TX, United States, (12)Virginia Polytechnic Institute and State University, Blacksburg, VA, United States, (13)Rice University, Physics and Astronomy, Houston, TX, United States, (14)NCAR, Boulder, CO, CO, United States
Abstract:
Dynamic and localized beads in the aurora have long been associated with subsequent explosive magnetotail activity. Simultaneous ground-based conjugate observations of these beads suggest a common magnetospheric driver. As a result auroral beads have received significant interest both as a diagnostic into the sparsely sampled magnetospheric processes leading up to substorms and as a possible causal agent due to their connection to unstable magnetotail configurations. Due to the disparity of scales between the global magnetosphere, near-Earth plasma sheet, and auroral ionosphere modeling investigations of these phenomena have been limited in scope.
We present the results of a first of its kind global simulation of the growth phase of synthetic substorm using our newly-developed global magnetosphere model, GAMERA, at its highest resolution, ~300 km in the central plasma sheet and ~30km in the auroral ionosphere. For the first time in a global model we are able to demonstrate the self-consistent formation and destabilization, due to ballooning-interchange instability, of a localized magnetic field minima in the near-Earth plasma sheet and that the resultant entropy bubbles drive field-aligned currents that manifest in the ionosphere as auroral beads. We will describe the role of flux redistribution, through a combination of dayside flux evacuation and flank Kelvin-Helmholtz vortices, on the destabilization of pre-existing marginally stable localized magnetic field minima. Finally we will describe the ionospheric manifestation of these magnetospheric processes, and the implications of ballooning-interchange unstable regions for auroral precipitation and localized conductance enhancements using coupled GAMERA-RCM simulations to incorporate drift physics.
